Field of the Invention
The present invention relates to an electrode assembly having excellent connective properties between electrode tabs and a battery cell and a device including the electrode assembly, and a method of manufacturing the electrode assembly, and more particularly, to an electrode assembly in which connective properties between electrode tabs are improved by arranging electrode tabs having the same polarity such that some thereof do not overlap one another on the same plane and a battery cell and a device including the electrode assembly, respectively, and a method of manufacturing the electrode battery.
Description of the Related Art
Due to development of technologies with respect to mobile devices and increased demand therefor, demand for second batteries has been rapidly increased. Among them, lithium secondary cell batteries having high energy intensity, high operating voltages and having excellent maintenance and lifespan properties are generally used not only in various mobile devices but also as energy sources for various electronic products.
Generally, lithium secondary cell batteries are formed to have a structure of sealing an electrode assembly and an electrolyte are provided in a battery case and are classified, according to external shapes thereof, into cylindrical batteries, square-shaped batteries, and pouch type batteries and may be classified, according to the form of the electrolyte, into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries. Due to the miniaturization of mobile devices, demand for square-shaped batteries and pouch type batteries having reduced thicknesses is increased, and particularly, pouch type batteries of which shapes thereof are easily able to be changed and having small weights have attracted attention.
On the other hand, electrode assemblies contained in battery cases may be classified, according to forms thereof, into a jelly-roll type structure, a stacked type structure, and a stacked and folded structure. Generally, jelly-roll type electrode assemblies are manufactured by coating metal foil used as current collectors with electrode active materials, pressing and cutting the same to be bands having desired widths and lengths, partitioning anodes and cathodes by using separation films, and then spirally winding the bands. Stacked type electrode assemblies are manufactured by vertically stacking an anode, a separation film, and a cathode. On the other hand, stacked and folded type electrode assemblies are manufactured by winding and folding electrode stacks formed of single electrodes or an anode/a separation film/a cathode by using a continuous long sheet type separation films.
On the other hand, electrode assemblies as described above include, for electrical connections, at least one anode tab and at least one cathode tab. Recently, as the number of electrodes included in electrode assemblies has increased, to provide higher degrees of capacitance, the number of electrode tabs included in electrode assemblies has also increased. Electrode tabs are generally connected so as not to be short-circuited before being packed into battery cases. Connected electrode tabs are contained in electrode terminals included in battery cases. To easily perform the connection and packing process as described above, in general, as shown in FIG. 1(b), all electrode tabs 1 having common polarities are arranged in common locations on a plane. However, as the number of electrode tabs included in electrode assemblies increases, when arranging electrode tabs according to general methods as described above, since thicknesses of stacks of electrode tabs may be increased, not only are the connective properties of electrode tabs deteriorated, but also, the sizes of electrode terminals for containing electrode tabs may be increased, to thereby spoil designed shapes of battery cells.
Also, in the case of consuming a large amount of energy to connect a large number of electrode tabs, excessive energy may be transferred to an electrode tab in a highest position, leading to the electrode tab being burned or to causing a deformational defect thereof, such as breaking. Otherwise, to prevent this, when reducing energy for the connection of electrode tabs, electrode tabs located in a lower position may not be fully connected, and may be separated or peeled off. FIG. 14 depicts a state in which electrode tabs are connected to an electrode stack by fifteen unit cells, stacked using a general method. In such configurations, electrode tabs are not perfectly connected, but separated, and some are burned. This means that it is impossible to fully connect electrode tabs to thick electrode assemblies having a large number of electrodes by using general methods.
Accordingly, it is necessary to develop a technology for improving connectivity between electrode tabs in electrode assemblies having a large number of stacks and of manufacturing battery cells having variously designed shapes.